1. Field of the Invention
The present invention relates to a computing system, a method of controlling the same, and a system management unit.
2. Description of the Related Art
Computing units for use in high-performance computing for computing weather forecast or tsunami propagation have more and more high-speed performance these years. Along with the speeded-up computing, the computing units handle a larger amount of data in the computing. Since the data for use in the high-performance computing and data resulting from the computing are stored in a storage, such a storage is required to have an extremely large capacity.
A computation in a high-speed computer is usually performed in batch processing based on a schedule or the like. When a computation is performed, three steps as follows are executed. In the first step, a data stored in a storage is transferred to a main memory of a computing unit. The step is hereinafter referred to as a staging to the computing unit. In the second step, a computation is executed using the transferred data as an input, and the outputted data is stored in the main memory. In the third step, the outputted data in the main memory is transferred to the storage and is stored therein. The step is hereinafter referred to as a destaging from the computing unit.
An increasing rate of a computing speed of a computing unit is allegedly larger than a decreasing rate of a price of a storage per unit capacity (hereinafter referred to as a bit cost). This means that a storage will cost a lot more, if a computing unit continues to have a configuration as it is, in which a data handled by the computing unit is all stored in a high-speed storage. To solve the problem, a configuration having a tiered structure of two storages is proposed. One of the two storages is a high-speed high-bit cost storage (hereinafter referred to as an online storage), and the other is a low-speed low-bit cost storage (hereinafter referred to as a nearline storage). Japanese Laid-Open Patent Application, Publication 2003-216460 (of which a US counterpart is US 2005-268062) and Japanese Laid-Open Patent Application, Publication 2006-195960 (of which a US counterpart is US 2006-0155950 A1) disclose how to control the tiered structure.
Japanese Laid-Open Patent Application, Publication 2003-216460 discloses a technique in which a data frequently accessed by a host (a computing unit) is transferred (migrated) to a storage having a high transfer rate or a high response rate. Thus an access to the data is speeded up.
Japanese Laid-Open Patent Application, Publication No. SHO 2006-195960 discloses a technique in which a threshold is established for a storage in advance, and, if a used capacity in the storage reaches or exceeds the threshold, a data is migrated to the other storage. Thus the capacity used in the storages is suitably controlled.
In the technique of Japanese Laid-Open Patent Application, Publication 2003-216460, however, an access to the data is speeded up by migrating a frequently accessed data to an online storage simply based on a frequency of the data accessed by a host, regardless of a computing schedule. This may bring about a problem as follows, if the technique is applied to a configuration of a high-speed computer. When a computing unit completes a computation and stores a resultant output data in an online storage, there may not be a sufficient free space therein, because a migration of the data is conducted regardless of the computing schedule. In this case, a destaging of the output data to a nearline storage is conducted instead, which decreases a performance of destaging the output data from the computing unit. Similarly, when an input data required for a computation is migrated from the nearline storage to the online storage, a shortage of a free space in the online storage may not allow the migration. In this case, a staging of the input data from the nearline storage to the computing unit may be conducted instead, which decreases a performance of staging the input data to the computing unit.
In the technique of Japanese Laid-Open Patent Application, Publication No. SHO 2006-195960, when a used space in an online storage reaches or exceeds a predetermined value, a certain data is migrated to a nearline storage to make a sufficient free space in the online storage. This may bring about a problem as follows, if the technique is applied to a configuration of a high-speed computer. A free space in the online storage is not used effectively due to lack of consideration of a computing schedule, which decreases a performance of a staging or a destaging.
The present invention has been made in an attempt to provide a computing system using tiered storages, capable of not decreasing a performance thereof, and having a large capacity and an excellent cost performance; a method of controlling the same; and a system management unit.